As a control unit for an articulated robot placed in a safety fence, a control unit which stops a robot when a door of a safety fence is in an open state, and then which stores the stop position and stop posture of the robot in a memory so that the articulated robot control unit can use, when resuming the operation, the stored stop position and the stop posture as the position and the posture of the robot is known. (See Japanese Unexamined Patent Application, Publication No. 2005-219138, for example.)
On the other hand, an articulated robot which can be operable under a situation in which a human exists in a vicinity of the articulated robot without using a safety fence (such as a robot which can work together with human) has come to be used for a variety of ways. (See Japanese Unexamined Patent Application, Publication No. 2017-074660, for example.) Such a robot control unit has a function of preventing objects from being caught by robot joints, a speed limit function, and a function of suspending robot operations when a sensor detects unsafe situations (safety stop function) so that the robot can operate under a situation in which a human exists in a vicinity of the robot.